Planar lightwave circuits (PLCs) are optical circuits laid out on a silicon wafer. PLCs, which typically contain one or more planar waveguides often used in arrayed waveguide gratings, are used as components in constructing an optical communication system. Optical communication systems permit the transmission of large quantities of information. With ever increasing internet traffic, greater demands are placed on optical communication systems, and their corresponding components.
A plurality of optical integrated circuits (OICs) including PLCs are typically fabricated on a single substrate or wafer. For example, a substrate may be fabricated with 30 to 40 OICs thereon. Individual OICs are isolated using a specialized saw to dice the substrate. However, OICs have a regular (consistent), non-rectangular geometry. Straight-line dicing using a saw consequently leads to the inefficient isolation of individual OICs from a substrate. Referring to FIG. 1, a substrate 100 with a plurality of PLCs 102 thereon is shown. Referring to FIG. 2, when individual PLCs 102 are isolated from the substrate 100 using a saw (square dicing), several PLCs 104 are destroyed while only one PLC 106 is recovered. Often times, two to four PLCs are destroyed for each PLC that is recovered.
There have been attempts to realize increased yields of OICs from optical component substrates using laser cutting techniques and water jet stream cutting techniques. These techniques are attractive because they in theory permit curvilinear cutting of non-rectangular shapes is possible.
Referring to FIG. 3, an OIC 120 diced using curvilinear cutting from a substrate containing a plurality of OICs thereon is shown (such as from the substrate shown in FIG. 1). Unfortunately, an OIC 110 cut in a curvilinear manner from a substrate often undesirably contains cracks 112 and chips 114. Such cracks 112 and chips 114 often constitute in fatal defects in the OIC 120 since the cracks 112 and chips 114 inhibit reliable operation of the optical components formed on the OIC.
Moreover, unlike machining metal substrates, OIC substrates and the components thereon are often made of monocrystalline silicon, silicon dioxide, various oxides and silicates, and other materials that are very brittle by nature. The brittle nature of such materials facilitates the formation of cracks and chips in the substrate or the components thereon during cutting. Thus, the propensity to form cracks and chips during curvilinear cutting in combination with the brittle nature of the OIC substrates leads to the low yield of OICs from OIC substrates. And since a plurality of OICs are fabricated in close proximity to one another, even small chips and cracks can render the OICs fatally defective.
There is an unmet need in the to art to improve the current yields of OICs/PLCs from substrates, and particularly to mitigate cracking and chipping when dicing the substrates containing a plurality of OICs/PLCs.